Nematic methyltolans

ABSTRACT

A nematic methyltolan of the formula: ##STR1## wherein R and R&#39; each represents independently a straight-chained alkyl group with 1 to 9 carbon atoms; n is an integer of 1 or 2; and ##STR2## has a trans (equatorial-equatorial) configuration.

BACKGROUND OF THE INVENTION

The present invention relates to a novel methyltolan type nematiccompound useful as an electro-optical display material.

The current market for liquid crystal displays is dominated by TN(twisted nematic) cells which fall under the category of field-effectcells. As reported by G. Bauer in Mol. Cryst. Liq. Cryst. 63, 45 (1981),these TN cells produce interference patterns on the cell surface thatcan impair the appearance of the cell and in order to prevent theoccurrence of such patterns, the product of birefringence (Δ_(n)), ofthe refractive index of liquid crystal material in the cell and the cellthickness, d (μm), must be fixed to a specified value. In commercialliquid display cells, the product Δ_(n).d is fixed to one of the values0.5, 1.0, 1.6 and 2.2. Since the value of Δ_(n).d may be fixed to thespecified value, the use of a liquid crystal marerial having a largevalue of Δ_(n) will lead to a decrease in d. If d is small, the responsetime of the cell is shortened in accordance with the well known relationταd². Therefore, a liquid crystal material having a large value of Δ_(n)is of vital importance in the fabrication of a liquid crystal displaycell that features quick response and the absence of any interferencepatterns.

Many of the commercially feasible liquid crystal materials availabletoday are usually prepared by mixing a few or more components made of acompound that has a nematic phase at or near room temperature and acompound that has a nematic phase in ranges higher than roomtemperature. Most of these mixed liquid crystals commercially used todayare required to have a nematic phase over the full temperature range of-30° to +65° C. As the application of liquid crystal display cellsincreases in diversity, it is desired to develop liquid crystalmaterials of large Δ_(n) that have a nematic phase in an even highertemperature range and to this end, nematic liquid crystal compoundshaving large Δ_(n) with high nematic to isotropic (N-I) transitiontemperatures are required.

With a view to meeting this need, the present inventors previouslyproposed ##STR3## as a nematic liquid crystal compound having a largeΔ_(n) and a high N-I transition temperature (Japanese Patent Application(OPI) No. 152427/85 corresponding to Ser. No. 692,570 now abandoned)(the term "OPI" as used herein refers to a "published unexaminedJapanese patent application"). However, as it turned out, this compoundis not high in miscibility with the nematic mixed liquid crystalscommonly used today, especially at low temperatures.

SUMMARY OF THE INVENTION

A principal object, therefore, of the present invention is to provide anovel nematic liquid crystal compound that has a large Δ_(n), a high N-Itransition temperature and good miscibility at low temperatures with thenematic mixed liquid crystals in common use today.

This object can be obtained by a compound of the following formula:##STR4## wherein R and R' each represents independently astraight-chained alkyl group with 1 to 9 carbon atoms; n is an integerof 1 or 2; and ##STR5## has a trans (equatorialequatorial)configuration.

DETAILED DESCRIPTION OF THE INVENTION

The compound (I) of the present invention can be produced by thefollowing reaction scheme, in which R and n in formula (II) and R' informula (III) have the same meanings as defined for formula (I):##STR6##

The compound of formula (II) is reacted with the compound of formula(III) in a solvent such as N,N-dimethylformamide in the presence ofbis(triphenylphosphine) palladium (II) chloride and cuprous iodide ascatalysts, so as to produce the compound of formula (I) of the presentinvention.

The transition temperatures of typical compounds of formula (I) producedby this method are noted in Table 1 below.

                  TABLE 1                                                         ______________________________________                                         ##STR7##                                                                     No.  R         R'      n    Transition temperature (°C.)               ______________________________________                                        1    n-C.sub.3 H.sub.7                                                                       CH.sub.3                                                                              1                                                                                   ##STR8##                                                                      ##STR9##                                         2    n-C.sub.4 H.sub.9                                                                       CH.sub.3                                                                              1                                                                                   ##STR10##                                                                     ##STR11##                                        3    n-C.sub.4 H.sub.9                                                                       CH.sub.3                                                                              2                                                                                   ##STR12##                                                                     ##STR13##                                                                     ##STR14##                                        ______________________________________                                         *Remarks:                                                                     C: crystalline phase;                                                         N: nematic phase;                                                             I: isotropic liquid phase;                                                    S: smectic phase.                                                        

The compounds of formula (I) of the present invention are nematic liquidcrystal compounds having a weak positive or negative value of anisotropyin dielectric constant. Therefore, if they are mixed with other nematicliquid crystal compounds having negative anisotropy in dielectricconstant, materials suitable for use in dynamic scattering mode displaycells can be produced. If the compounds of formula (I) are mixed withthe other nematic liquid crystal compounds having positive or negativeanisotropy in dielectric constant, materials suitable for use intwisted-nematic display cells may be obtained.

Illustrative compounds that can be mixed with the compounds of formula(I) to make preferable materials for use in liquid crystal display cellsare listed below: 4'-substituted phenyl 4-substituted benzoate,4'-substituted phenyl 4-substituted cyclohexanecarboxylate,4'-substitued biphenyl 4-substituted cryclohexanecarboxylate,4'-substituted phenyl 4-(4-substituted cyclohexanecarbonyloxy)benzoate,4'-substituted phenyl 4-(4-substituted cyclohexyl)benzoate,4'-substituted cyclohexyl 4-(4-substituted cyclohexyl)benzoate,4-substituted 4'-substituted biphenyl, 4-substituted 4'-substitutedcylohexane, 4-substituted 4'-substituted terphenyl, 4-substitutedbiphenyl 4'-substituted cyclohexane, and 2-(4-substitutedphenyl)-5-substituted pyrimidine.

Table 2 lists the N-I transition temperature and birefringences (Δ_(n))of mixed liquid crystals composed of 85 wt% of liquid-crystal host (A)and 15 wt% of compound No. 1, 2 or 3 of formula (I) shown in Table 1.Table 2 also shows the N-I transition temperature and Δ_(n) ofliquid-crystal host (A) for comparison. Liquid-crystal host (A) iscurrently in extensive use as a nematic liquid crystal material and iscomposed of the following components: ##STR15##

                  TABLE 2                                                         ______________________________________                                                    N-I transition                                                                temperature (°C.)                                                                 Δ.sub.n (-)                                      ______________________________________                                        (A)           54.0          0.0917                                            (A) + No. 1   70.8         0.116                                              (A) + No. 2   69.3         0.115                                              (A) + No. 3   90.9         0.113                                              ______________________________________                                    

One will understand from Table 2 that compounds of formula (I) increasethe N-I transition temperature of the liquid-crystal host to levels thatare satisfactory for practical applications and that they also achievesignificant increases in Δ_(n).

These advantages of the present invention will also become apparent fromthe following comparative experiment. A known compound having theformula: ##STR16## which is similar to formula (I) was developed with aview to increasing the N-I transition temperature and Δ_(n) of a mixedliquid crystal. This compound had 6% solubility in liquid-crystal host(A) at -30° C. The resulting mixed liquid crystal had a N-I transitionpoint of 62.1° C. and Δ_(n) of 0.01. In contrast, compound No. 2 of thepresent invention having the formula: ##STR17## had 13% solubility inliquid-crystal host (A) at -30° C., and the resulting mixed liquidcrystal had a N-I transition point of 67.2° C. and Δ_(n) of 0.112.

These results suggest that compounds of formula (I) within the scope ofthe present invention which can be incorporated in a liquid-crystal hostin greater amounts than a representative known analogous compound andare effective in achieving marked increases in the N-I transitiontemperature and Δ_(n) of the mixed liquid crystal.

The following examples are provided for the purpose of furtherillustrating the present invention but are in no way to be taken aslimiting.

EXAMPLE 1

A compound of the formula ##STR18## was dissolved in 400 ml ofN,N-dimethylformamide in an amount of 39.6 g (0.120 mol). To theresulting solution were added 240 mg (0.34 mmol) ofbis(triphenylphosphine) palladium (II) chloride, 600 mg (3.1 mmol) ofcuprous iodide and 100 ml of diethylamine. To the mixture, 15.6 g (0.120mol) of 2,4-dimethylphenylacetylene was added with stirring. Theresulting mixture was reacted at room temperature for 20 hours. Thereaction mixture was rendered acidic by being added to a cold diluteaqueous solution of hydrogen chloride (HCl) with stirring. The reactionproduct was extracted with toluene and the extract was washed withwater, dried and freed of toluene by distillation.

The recovered reaction product was recrystallized from ethyl acetate toobtain 28.5 g (0.0828 mol) of the following compound in pure form:##STR19##

Yield: 69.0%

Transition temperature: 77° C. (C→N); 174° C. (N⃡I).

By similar procedures, the following compound was obtained: ##STR20##

Yield: 67.1

Transition temperature: 65° C. (C→N); 163° C. (N⃡I).

Additional compounds that can be produced by similar procedures arelisted in Table 3.

Among the compounds listed in Table 3, those wherein R' is a methylgroup are preferred.

                  TABLE 3                                                         ______________________________________                                         ##STR21##                                                                    No.          R             R'                                                 ______________________________________                                         4           CH.sub.3      CH.sub.3                                            5           C.sub.2 H.sub.5                                                                             CH.sub.3                                            6           n-C.sub.5 H.sub.11                                                                          CH.sub.3                                            7           n-C.sub.6 H.sub.13                                                                          CH.sub.3                                            8           n-C.sub.7 H.sub.15                                                                          CH.sub.3                                            9           n-C.sub.8 H.sub.17                                                                          CH.sub.3                                           10           n-C.sub.9 H.sub.19                                                                          CH.sub.3                                           11           CH.sub.3      C.sub.2 H.sub.5                                    12           C.sub.2 H.sub.5                                                                             C.sub.2 H.sub.5                                    13           n-C.sub.3 H.sub.7                                                                           C.sub.2 H.sub.5                                    14           n-C.sub.4 H.sub.9                                                                           C.sub.2 H.sub.5                                    15           n-C.sub.5 H.sub.11                                                                          C.sub.2 H.sub.5                                    16           n-C.sub.6 H.sub.13                                                                          C.sub.2 H.sub.5                                    17           n-C.sub.7 H.sub.15                                                                           C.sub.2 H.sub.5                                   18           n-C.sub.8 H.sub.17                                                                          C.sub.2 H.sub.5                                    19           n-C.sub.9 H.sub.19                                                                          C.sub.2 H.sub.5                                    20           CH.sub.3      n-C.sub.3 H.sub.7                                  21           C.sub.2 H.sub.5                                                                             n-C.sub.3 H.sub.7                                  22           n-C.sub.3 H.sub.7                                                                           n-C.sub.3 H.sub.7                                  23           n-C.sub.4 H.sub.9                                                                           n-C.sub.3 H.sub.7                                  24           n-C.sub.5 H.sub.11                                                                          n-C.sub.3 H.sub.7                                  25           n-C.sub.6 H.sub.13                                                                          n-C.sub.3 H.sub.7                                  26           n-C.sub.7 H.sub.15                                                                          n-C.sub.3 H.sub.7                                  27           n-C.sub.8 H.sub.17                                                                          n-C.sub.3 H.sub.7                                  28           n-C.sub.9 H.sub.19                                                                          n-C.sub.3 H.sub.7                                  29           CH.sub.3      n-C.sub.4 H.sub.9                                  30           C.sub.2 H.sub.5                                                                             n-C.sub.4 H.sub.9                                  31           n-C.sub.3 H.sub.7                                                                           n-C.sub.4 H.sub.9                                  32           n-C.sub.4 H.sub.9                                                                           n-C.sub.4 H.sub.9                                  33           n-C.sub.5 H.sub.11                                                                          n-C.sub.4 H.sub.9                                  34           n-C.sub.6 H.sub.13                                                                          n-C.sub.4 H.sub.9                                  35           n-C.sub.7 H.sub.15                                                                          n-C.sub.4 H.sub.9                                  36           n-C.sub. 8 H.sub.17                                                                         n-C.sub.4 H.sub.9                                  37           n-C.sub.9 H.sub.19                                                                          n-C.sub.4 H.sub.9                                  38           CH.sub.3      n-C.sub.5 H.sub.11                                 39           C.sub.2 H.sub.5                                                                             n-C.sub.5 H.sub.11                                 40           n-C.sub.3 H.sub.7                                                                           n-C.sub.5 H.sub.11                                 41           n-C.sub.4 H.sub.9                                                                           n-C.sub.5 H.sub.11                                 42           n-C.sub.5 H.sub.11                                                                          n-C.sub.5 H.sub.11                                 43           n-C.sub.6 H.sub.13                                                                          n-C.sub.5 H.sub.11                                 44           n-C.sub.7 H.sub.15                                                                          n-C.sub.5 H.sub.11                                 45           n-C.sub.8 H.sub.17                                                                          n-C.sub.5 H.sub.11                                 46           n-C.sub.9 H.sub.19                                                                          n-C.sub.5 H.sub.11                                 47           CH.sub.3      n-C.sub.6 H.sub.13                                 48           C.sub.2 H.sub.5                                                                             n-C.sub.6 H.sub.13                                 49           n-C.sub.3 H.sub.7                                                                           n-C.sub.6 H.sub.13                                 50           n-C.sub.4 H.sub.9                                                                           n-C.sub.6 H.sub.13                                 51           n-C.sub.5 H.sub.11                                                                          n-C.sub.6 H.sub.13                                 52           n-C.sub.6 H.sub.13                                                                          n-C.sub.6 H.sub.13                                 53           n-C.sub.7 H.sub.15                                                                          n-C.sub.6 H.sub.13                                 54           n-C.sub.8 H.sub.17                                                                          n-C.sub. 6 H.sub.13                                55           n-C.sub.9 H.sub.19                                                                          n-C.sub.6 H.sub.13                                 56           CH.sub.3      n-C.sub.7 H.sub.15                                 57           C.sub.2 H.sub.5                                                                             n-C.sub.7 H.sub.15                                 58           n-C.sub.3 H.sub.7                                                                           n-C.sub.7 H.sub.15                                 59           n-C.sub.4 H.sub.9                                                                           n-C.sub.7 H.sub.15                                 60           n-C.sub.5 H.sub.11                                                                          n-C.sub.7 H.sub.15                                 61           n-C.sub.6 H.sub.13                                                                          n-C.sub.7 H.sub.15                                 62           n-C.sub.7 H.sub.15                                                                          n-C.sub.7 H.sub.15                                 63           n-C.sub.8 H.sub.17                                                                          n-C.sub.7 H.sub.15                                 64           n-C.sub.9 H.sub.19                                                                          n-C.sub.7 H.sub.15                                 65           CH.sub.3      n-C.sub.8 H.sub.17                                 66           C.sub.2 H.sub.5                                                                             n-C.sub.8 H.sub.17                                 67           n-C.sub.3 H.sub.7                                                                           n-C.sub.8 H.sub.17                                 68           n-C.sub.4 H.sub.9                                                                           n-C.sub.8 H.sub.17                                 69           n-C.sub.5 H.sub.11                                                                          n-C.sub.8 H.sub.17                                 70           n-C.sub.6 H.sub.13                                                                          n-C.sub.8 H.sub.17                                 71           n-C.sub.7 H.sub.15                                                                          n-C.sub.8 H.sub.17                                 72           n-C.sub.8 H.sub.17                                                                          n-C.sub.8 H.sub.17                                 73           n-C.sub.9 H.sub.19                                                                          n-C.sub.8 H.sub.17                                 74           CH.sub.3      n-C.sub.9 H.sub.19                                 75           C.sub.2 H.sub.5                                                                             n-C.sub.9 H.sub.19                                 76           n-C.sub.3 H.sub.7                                                                           n-C.sub.9 H.sub.19                                 77           n-C.sub.4 H.sub.9                                                                           n-C.sub.9 H.sub.19                                 78           n-C.sub.5 H.sub.11                                                                          n-C.sub.9 H.sub.19                                 79           n-C.sub.6 H.sub.13                                                                          n-C.sub.9 H.sub.19                                 80           n-C.sub.7 H.sub.15                                                                          n-C.sub.9 H.sub.19                                 81           n-C.sub.8 H.sub.17                                                                          n-C.sub.9 H.sub.19                                 82           n-C.sub.9 H.sub.19                                                                          n-C.sub.9 H.sub.19                                 ______________________________________                                    

EXAMPLE 2

The procedures of Example 1 were repeated except that the compound ofthe formula ##STR22## was replaced by 50.9 g (0.120 mol) of a compoundof the formula ##STR23## The compound thus obtained had the followingformula: ##STR24##

Yield: 64.1%

Transition temperature: 125° C. (C→S); 162° C. (S⃡N); <300° C. (N⃡I).

By similar procedures, a variety of compounds having the general formula##STR25## can be produced. In this formula, R and R' may be combined inany of the ways that are specifically indicated in Example 1.

By repeating the procedures of Example 1 except that2,4-di-methylphenylacetylene was replaced by a3,4-di-methylphenylacetylene having the general formula ##STR26## can beproduced. In this formula, R and R' may be combined in any of the waysthat are specifically indicated in Example 1.

By repeating the procedures of Example 1 except that the compound of theformula ##STR27## was replaced by a compound of the formula ##STR28##and that 2,4-dimethylphenylacetylene was replaced by a3-methyl-4-alkylphenylacetylene, compounds of the general formula##STR29## could be produced. In this formula, R and R' may be combinedin any of the ways that are specifically indicated in Example 1.

The novel nematic liquid crystal compound of the present invention has ahigh N-I transition temperature and a large Δ_(n) as well. Therefore,the N-I transition temperature and Δ_(n) of a known mixed liquid crystalcan be increased by mixing it with the compound of the presentinvention. In addition, compared with a known structuraltemperature andΔ_(n) of a known mixed liquid crystal can be increased by mixing it withthe compound of the present invention. In addition, compared with aknown structurally analogous compound, the compound of the presentinvention has a great solubility in known mixed liquid crystals at lowtemperatures and, hence, mixed liquid crystals having even higher N-Itransition temperatures and Δ_(n) values can be prepared.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A compound of the general formula: ##STR30##wherein R and R' each independently represent a straight-chained alkylgroup with 1 to 9 carbon atoms; n is an integer of 1 or 2; and ##STR31##has a trans (equatorial-equatorial) configuration.
 2. The compound ofclaim 1, wherein the compound is represented by formula: ##STR32## 3.The compound of claim 1, wherein the compound is represented by formula:##STR33##
 4. The compound of claim 1, wherein the compound isrepresented by formula: ##STR34##
 5. The compound of claim 1, whereinthe compound is represented by formula: ##STR35##
 6. The compound ofclaim 1, wherein the compound is represented by formula: ##STR36## 7.The compound of claim 1, wherein the compound is represented by formula:##STR37##
 8. The compound of claim 1, wherein the compound isrepresented by formula: ##STR38##
 9. The compound of claim 1, whereinthe compound is represented by formula: ##STR39##
 10. The compound ofclaim 1, wherein the compound is represented by formula: ##STR40## 11.The compound of claim 1, wherein the compound is represented by formula:##STR41##
 12. The compound of claim 1, wherein the compound isrepresented by formula: ##STR42##
 13. The compound of claim 1, whereinthe compound is represented by formula: ##STR43##